The article describes an experiment conducted on maiden apple trees of selected cultivars growing in a nursery. The aim of the study was to investigate how the foliar application of four biostimulants (Aminoplant 0.4%, Biamino Plant 0.2%, Bispeed 0.2% and Fylloton 0.4%) and two fertilisers (Basfoliar 6-12-6 and Basfoliar 12-4-6+S both at a concentration of 0.5%) affected the growth of the trees cultivated with the mineral fertilisation reduced by half. The plants were sprayed with the preparations and fertilisers four times at three-week intervals, between late May and late July. Selected parameters of the plants’ physiological processes were also assessed: net photosynthetic rate (Pn), transpiration rate (E), stomatal conductance (C) and intracellular CO2 (I). The foliar application of all the biostimulants and fertilisers significantly improved the growth of the maiden apple trees. The lowest values of the plant growth parameters were noted in the control combination, which was treated with a full dose of mineral fertiliser. The foliar spraying of the apple trees particularly improved the total length and number of side shoots and the fresh weight of maiden apple trees. The apple tree cultivars differed in their growth parameters, and the influence of individual foliar treatments was not conclusive. The foliar application of selected preparations intensified the leaf transpiration coefficient and the internal concentration of carbon dioxide, but it did not increase the net photosynthesis intensity or stomatal conductance.

The experiment compared the use of a dose of mineral fertilisation reduced by half in a nursery, which was replaced by foliar treatment with biostimulants and fertilisers. The control combination was a full dose of mineral fertilisation without foliar treatments. The half dose of mineral fertiliser applied into the soil decreased its acidity and salinity. At the same time, it decreased the soil content of macro- and micronutrients, except for calcium and iron. In most cases the simultaneous foliar application of the four biostimulants tested in our experiment reduced the content of macronutrients in the leaves of maiden apple trees, except for calcium. On the other hand, it increased the iron (28.2% average) and manganese (24.8% average) levels in the leaves but reduced the levels of zinc (11.8% average) and copper (25% average). The foliar application of two fertilisers increased the leaf contents of phosphorus (12% average) and calcium (9.3% average). One of the fertilisers also increased the leaf contents of potassium, magnesium, and micronutrients.